The thymus in immunity and in malignancy.

The thymus is an essential organ for the generation of the adaptive immune system. By now, the cellular selection events taking place in ongoing life before sexual maturity have been worked out even at the molecular level, and thus thymic lymphocyte development represents one of the best-studied systems in mammalian development. Because thymic lymphocyte development involves ample proliferation and generation of new cells, it is not astonishing that the thymus also represents an organ where malignancy can develop. In this Masters of Immunology primer, the development of lymphocytes and the role of intracellular Notch 1 and cyclins in lymphocytic malignancy are reviewed, offering new therapeutic possibilities.